Ball joint

ABSTRACT

A ball joint, in particular for the wheel suspension systems of motor vehicles, an external, essentially cylindrical housing, an internal joint piece with a pin supporting a ball section and a bearing race surrounding the ball section, is retained in the cylindrical housing and has annular seals on both sides of the pin ends. In order to achieve a hydraulic damping function, annular gaps are provided about the pin adjacent to the ball section, filled directly or indirectly with a damping fluid.

FIELD OF THE INVENTION

The invention relates to a ball joint, in particular for wheelsuspensions of motor vehicles, as specified in the claims.

BACKGROUND OF THE INVENTION

A ball joint such as this is disclosed in DE 42 07 602 A1, for example.Such joints, which are rotatable about the central axis of the ball andpivotable through a limited pivoting angle, are often used as suspensionjoints in wheel suspensions of motor vehicles. In addition to theirreliability and smoothness of operation, such ball joints are assigned aspecific damping function for eliminating vibrations.

SUMMARY OF THE INVENTION

The object of the invention is to propose a generic ball joint which isadvantageous from the viewpoint of structure and production technologyand which performs a specific damping function.

It is claimed for the invention that this object is attained by thecharacteristics specified in the primary claims. Advantageousdevelopments of the invention are set forth in the many dependentclaims.

It is proposed in accordance with the invention that annular gaps filleddirectly or indirectly with a damping fluid be formed around the ballpivot adjacent to the ball section. The damping fluid, preferably one ofhigh viscosity, both ensures smooth operation of the ball joint nearlyfree of wear and at the same time effectively damps vibrations aroundthe center of the ball within a specific frequency range, in particularwhen the joint is used as journal bearing in wheel suspensions of motorvehicles. The damping fluid may possess electrorheologic ormagnetorheologic properties.

In a structurally favorable embodiment the annular gaps may be boundedessentially by annular extensions on the bearing ring enclosing the ballsection. By preference the length of the annular gap should be greaterthan its width by a factor of 3 in order to ensure adequate dampingoperation. In addition, the annular gaps preferably may be formedbetween tapering ball pivot sections and correspondingly configuredextensions on the bearing ring; this results in rugged pivot structureand structurally more favorable sealing between the ball pivot ends andthe outer cylindrical housing of the ball joint.

An indirect layout in which annular tubes filled with damping fluid areused in the annular gaps is proposed as an alternative to directintroduction of the damping fluid into the annular gaps. Specificdamping properties of the ball joint may also be imparted by shaping ofthe annular tubes (e.g., by use of fabric reinforcements) and byfunctional separation of lubrication of the joint (e.g., with grease)and the damping medium.

The annular tubes may be seated in prismatic guide rings of thecylindrical housing and butt against annular collars of the ball pivotsections formed in the area of the tubes. When the ball joint is free ofload this results in more or less linear contact between the ball pivotsections and the tubes, contact which does not impair smooth operationof the ball joint and also ensures a specified damping behavior.

Use of a damping fluid possessing electrorheologic or magnetorheologicproperties makes it possible to create a continuously variable dampingcharacteristic.

Such use permits configuration of a ball joint with controllable torsiondamping (driving-dependent change in the damping property) which may beemployed, for example, to reduce vibration problems in multiple-rodaxles.

A damping fluid characterized by rheologic action presents the advantageof rapid response behavior (damping control almost in real time, so thatdamping in the area of the natural wheel frequency as well is possible).The damping characteristic of the rheologic fluid may be modified bymeans of a control device and the damping characteristic of a ball jointcontrolled accordingly.

BRIEF DESCRIPTION OF THE DRAWINGS

Two exemplary embodiments of the invention are described in greaterdetail in what follows. The accompanying drawing, in the form ofdiagrams, shows in

FIG. 1, a longitudinal section through a ball joint for wheelsuspensions of motor vehicles with specified annular gaps filled withdamping fluid on both sides of the ball section; and

FIG. 2, another longitudinal section through a ball joint with hosesfilled with a damping fluid mounted in annular gaps on both sides of theball section.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a ball joint designated as 10 which consists essentially ofan outer cylindrical housing 12, an inner rotation-symmetric joint pivotmember 14 comprising ball pivot shaft portions 18, 20 and a ball section16 and a bearing ring 22 enclosing the ball section 16.

The joint element 14 has a through opening 24 by means of which thiselement may be fastened by means of a screw to a wheel carrier of awheel suspension of a motor vehicle. The cylindrical housing 12 may alsobe rigidly connected by a method not illustrated to a guide rod of thewheel suspension. The housing 12 and the joint element 14 are madeconventionally of metal, while the bearing ring 22 is made of a suitableplastic such as polymethylene oxide.

The bearing ring 22 enclosing the ball section 16 is designed to be oftwo parts, with a plane of separation 22 a extending vertically relativeto the joint central axis 26, and is kept axial in the cylindrical axis12 both on the circumference side and both on an annular collar 28 onone side and on a screwed-in clamping ring 30 on the other.

Annular seals 32 which seal the ball joint 10 from the exterior, butwithout impairing the required pivotability of the inner joint element14 about the ball section center point 34, are mounted between thecylindrical sections of the ball pivot 18, 20 and the front ends of thecylindrical housing 10.

In addition, conical ball pivot sections 18 a, 20 a tapering toward theends of the ball pivot are formed between the cylindrical sections ofthe ball pivot 18, 20 and the ball section 16. In conjunction withannular extensions 36,38 also tapering internally, these ball pivotsections form on the bearing ring 22 annular gaps 40,42 having a lengthl and a mean width b, to which the statement l≧3b applies.

The annular gaps 40, 42 are filled with a high-viscosity incompressibledamping fluid or oil which is tightly enclosed between the seals 32inside the ball joint 10 and which simultaneously acts as a lubricant.

When vibration of the ball joint 10 is excited around the ball sectioncenter point 34, the annular gaps 40,42 narrow and widen on both sidesof the ball section 16 respectively and in the process displace thedamping fluid in the circumferential direction, this resulting inperformance of a specified damping function. The damping properties maybe determined by the configuration of the annular gaps 40, 42 and thestructure of the annular seals 32 respectively.

In order to avoid repetition, the ball joint 50 shown in FIG. 2 isdescribed only to the extent that it differs from the ball joint 10shown in FIG. 1. Functionally identical parts are provided with the samereference numbers.

The ball joint 50 in turn has a cylindrical outer housing 52, aninternal joint element 54 with a ball section 56 and adjoining ballpivot 58, 60.

The bearing ring 62 enclosing the ball section 56 is retained axiallyone on side by an annular collar 64 of the housing 52 and by ascrewed-in clamping ring 66 on the other.

Adjoining the foregoing a guide ring 68, 70 prismatic in cross-sectionis fastened in the housing 52 (is pressed in or screwed in).

Spherical annular collars 72, 74 are formed on the ball pivots 58, 60radially opposite the guide rings 68, 70.

Fabric-reinforced elastic rubber tubes 80, 82 filled with ahigh-viscosity damping fluid are formed in the annular gaps 76, 78between the guide rings 68,70 and the ball pivots 58, 60.

The tubes 80,82 are seated to approximately half their circumference inthe prismatic guide rings 68, 70 and on the other side rest against thespherical annular collars 72, 74 of the ball pivots 58, 60.

The annular gaps 76, 80, in turn, are sealed from the exterior by theannular seals 32.

The damping properties of the ball joint 50 are determined chiefly onthe basis of the configuration of the tubes 80, 82, the guide rings 68,70, the ball pivots 58, 60 with or without the annular collars 72, 74,and, lastly, the seals 32. Lubricant and damping medium may be specifiedand employed separately.

If a damping fluid possessing an electrorheologic property is used, itis necessary to use an electric insulating layer in the through opening(24) of the joint element (14, 54). Similarly, the cylindrical housing(12, 52) must be enclosed in an electrically insulating layer (110). Theinsulating layer may be, for example, in the form of an electricallyinsulating material (such as a plastic). This is necessary in order toprevent a short circuit when electric control voltage is applied to theelectrorheologic fluid. The electric control voltage is provided by acontrol device (100).

The electric insulating layer may be dispensed with when amagnetorheologic fluid is used. A magnetic field which permits controlof the damping characteristic of the ball joint is generated in thecavities through which damping fluid flows, by way of an external powersupply (120) applied to an electric coil in the joint element (14, 54)or in the cylindrical housing (12,52).

1. A ball joint for a wheel suspension system of a motor vehicle, saidball joint comprising: a housing having an opening at each end defininga cavity therebetween and comprising an annular collar at one endthereof and an axially aligned threaded section at the other endthereof; a pivot member extending through said housing having a ballsection disposed within said cavity and a pair of axially opposed pivotshaft portions, each pivot shaft portion extending through one of saidopenings; an annular threaded clamping ring threaded into said threadedsection of said housing; a first annular bearing disposed between saidpivot member and said housing having a first portion engaging a firstaxial portion of said ball section and a first annular extension axiallyextending from said first portion of said first bearing and engagingsaid threaded clamping ring, said first annular extension surroundingone of said pivot shaft portions and forming an annular gap between saidhousing and said one pivot shaft portion; a second annular bearingdisposed between said pivot member and said housing having a firstportion engaging a second axial portion of said ball section and asecond annular extension axially extending from the first portion ofsaid second bearing and engaging said annular collar, said secondannular extension surrounding the other of said pivot shaft portions andforming an annular gap between said housing and said other pivot shaftportion; a pair of annular seals, each seal disposed between andengaging a respective one of said pivot shaft portions and a respectiveone of said threaded clamping ring and said one housing end comprisingsaid annular collar, each seal cooperating with a respective one of saidfirst and second annular extensions to form a sealed annular chamberwithin a respective one of said annular gaps; and a damping fluiddisposed in each of said chambers in direct contact with said ballsection.
 2. A ball joint according to claim 1, wherein the dimension ofeach of said annular chambers in an axial direction is at least threetimes greater than the dimension of such chamber in a radial direction,relative to an axis of said chamber.
 3. A ball joint to claim 1, whereinopposed wall portions of each of said annular chambers arefrusto-conically configured, diverging in a direction away from saidball section.
 4. A ball joint according to claim 1, wherein said dampingfluid possesses electrorheological properties.
 5. A ball joint accordingto claim 4, including a controlled electric field imposed on saiddamping fluid.
 6. A ball joint according to claim 1, wherein saiddamping fluid possesses magnetorheological properties.
 7. A ball jointaccording to claim 6, including a controlled magnetic field imposed onsaid damping fluid.
 8. A ball joint according to claim 1, wherein saidsealing members are formed of a plastic material.